It's possible, but it's not designed to. It was designed to run under init, as a daemontools clone. Explained further here: http://smarden.org/pape/djb/daemontools/noinit.html

"In contrary to Richard Gooch, I suggest not to implement service dependencies and runlevel handling in the Unix process no 1, /sbin/init, keep it small and simple, that is why I wrote the runit package"